On Tue, Jun 12, 2012 at 10:34 AM, Myron Stowe <mstowe@xxxxxxxxxx> wrote: > On Mon, 2012-06-11 at 19:52 -0700, Bjorn Helgaas wrote: >> On Fri, Jun 1, 2012 at 2:16 PM, Myron Stowe <myron.stowe@xxxxxxxxxx> wrote: >> > The following series introduces PCI Express 'capability structure' >> > related cleanup, fixes, and optimizations. >> > >> > Patch 1/4 changes pci_ltr_supported() to a static routine. >> > >> > Patch 2/4 removes redundant checking in various PCI Express features as >> > suggested by Bjorn Helgaas in >> > http://marc.info/?l=linux-pci&m=130463494319762&w=2 >> > >> > There is a similar idiom in use that could be similarly be re-factored: >> > if (!pci_is_pcie(dev)) >> > return; >> > >> > pos = pci_find_ext_capability(dev, ...); >> > if (!pos) >> > return; >> > >> > At first it seemed incorrect to remove the redundant call of >> > pci_is_pcie() in these cases as a PCI or PCI-X (< 2.0) device may be >> > involved. In such cases an "extended capability" list would not exist, >> > as it was not introduced until PCI-X 2.0, and accesses outside of the >> > device's configuration space would be attempted. However, upon further >> > review of pci_find_ext_capability() it looks as if such accesses would >> > be handled correctly due to the short-circuiting logic involved - >> > >> > if (pci_read_config_dword(dev, pos, &header) != PCIBIOS_SUCCESSFUL) >> > return 0; >> > >> > As such, I'll entertain comments as to whether or not we should also >> > make similar removals of pci_is_pcie() in these cases. >> > >> > Patch 3/4 introduces pci_pcie_cap2() for use in v2 capability related >> > feature code. The makeup of Express' capability structure varies >> > substantially between v1 and v2. >> > >> > There is still some redundancy in PCIe v2 capabilities checking related >> > to the Latency Tolerance Reporting (LTR) feature routines that likely >> > could be re-factored further; please feel free to respond with ideas. >> > >> > Patch 4/4 makes a minor optimization to the saving and restoring of >> > PCI Express capability structures. >> > >> > Seems like the same type of optimization could be done to remove the >> > 'if (pcie_cap_has_lnkctl(dev->pcie_type, flags))' check. According to >> > section 7.8 "PCI Express Capability Structure" of the PCI Express 1.0a >> > specification: >> > >> > "Figure 7-10 details allocation of register fields in the PCI >> > Express Capability structure. The PCI Express Capabilities, >> > Device Capabilities, Device Status/Control, Link Capabilities, >> > and Link Status/Control registers are required for all PCI >> > Express devices. Endpoints are not required to implement >> > registers other than those listed above and terminate the >> > capability structure." >> > >> > There may have been some early Express devices that did not properly >> > follow the specification which required the introduction of >> > 'pcie_cap_has_lnkctl()' so I did not make the additional optimization. >> > --- >> > >> > Myron Stowe (4): >> > PCI: Remove redundant capabilities checking in pci_{save,restore}_pcie_state >> > PCI: Add pci_pcie_cap2() check for PCIe feature capabilities >= v2 >> > PCI: Remove redundant checking in PCI Express capability routines >> > PCI: make pci_ltr_supported static. >> >> I added Don's acks, made a couple minor changes he suggested, removed >> the static pci_ltr_supported() function declaration (unnecessary, >> AFAICS), and pushed these to: >> >> http://git.kernel.org/?p=linux/kernel/git/helgaas/pci.git;a=shortlog;h=refs/heads/topic/stowe-cap-cleanup >> >> If everything looks right to you, I'll merge it into "next" tomorrow. >> Thanks for doing this; I think it's some nice cleanup and will make >> things safer and easier to understand. > > Looks good - thanks to both Don and yourself for the suggestions and > changes to make the patch headers more comprehensible with respect to > the capabilities structure versions. Great, I merged that topic branch to "next" and pushed it. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
